IMHO, you will only know that in hindsight. If you meet someone you like to be with, and who enjoys your company for more than a few minutes, make plans to meet up again. If she agrees and you still like to be together, do it again. If it continues to be a fulfilling experience, make it regular. If things go south (no offense to those from that part of the earth) then let go. But only when you have experienced and gotten to know each other will you know if it was the "right time" and if she/he is the "right person."